The design of recreational
boats, including sailboats, leaves the
concept of
reliability and
safety aside while servicing glitz and gloss. Among the most unreliable of the traditional ways things are done are the
thru hull fittings. Any discharge line should be ABOVE the waterline so it cannot leak. Such outlets also allow the boater to see if something is working properly, say the
refrigeration heat exchanger (a better way to plumb this
service is to incorporate the refrigeration/air conditioning
heat exchanger into the
keel cooler.) An intake line should tap into a central, very strong,
thru hull with a large external
screen and internal shut off valve that is easily accessed and closed. This intake should be in a sump with its top above the
water line and equipped with a
water alarm to reveal
leaks immediately. There only needs to be one intake line for water rmakers, toilets, etc. Of course, the
bilge should also feature a high water
alarm. One major source of sinking caused by hull penetrations is the engine heat exchanger feed line.
Commercial boats usually use a
keel cooler because it is sealed and does not require an extra and unreliable, rubber impeller type
pump. Also, I would not have an internal heat exchanger system on my sailboat because of the problems with a wet
exhaust. Fitting failures with a wet
exhaust are a great way to sink your boat; however, most boaters are unaware of the fact thaT the long-term effects of saltwater vapors invading the cylinders of the
diesel engine are extremely damaging. It is downright stupid to put unprotected cast iron and
steel in contact with the vapors of hot saltwater - as happens with the typical small sailboat
diesel. Wet exhausts are popular but both unnecessary and dangerous. Properly muffled and with a tall enough exhaust pipe, a dry exhaust is extremely durable, quiet, and protective of the engine. Only the exhaust manifold itself need have a water jacket to satisfy the law. Beyond the manifold, simple
insulation and a metal outside tube is sufficient to keep heat from being a problem. The outer tube is usually made large enough to create a
draft that passively ventilates the engine room - another plus. Lastly, a dry and easily seen exhaust allows the boater to see the exhaust gasses and note any mechanical problems with the engine. You can tell a lot from what is coming out the exhaust. A hull is designed to keep water out of a boat and defeating this purpose with a bunch of thru hull fittings is kinda dumb. A composting or incinerating head is better than a pump-out type for many reasons, not the least of which is that
plumbing salt water around inside the boat is hazardous. Galley sink drains have sunk a lot of boats, my father's for one. These should feature a spring-loaded shutoff valve that must be operated to drain the sink. This type of valve may annoy the cook but they beat swimming for shore in the middle of the night. Just like when you leave your house for any substantial period of time, you should shut off the water - all below thru hull fittings - every time you shut down the boat. The currently popular way of placing shut off valves in difficult-to-reach places only encourages people to fail to protect their boat by shutting off the thru hull when they leave. Having no hull penetrations below the waterline is the ideal but the
shaft seal and the
single thru hull for the
keel cooler are pretty much impossible to avoid.
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